A projection exposure apparatus including an illumination system is known from US 2011/0 014 799 A1, WO 2009/121 438 A1, US 2009/0 174 876 A1, U.S. Pat. No. 6,438,199 B1 and U.S. Pat. No. 6,658,084 B2. An EUV light source is known from DE 103 58 225 B3 and U.S. Pat. No. 6,859,515 B. Further component parts for EUV projection lithography are known from US 2003/0002022 A1, DE 10 2009 025 655 A1, U.S. Pat. No. 6,700,952 and US 2004/0140440 A. Further references from which an EUV light source is known are found in WO 2009/121 438 A1. EUV illumination optical units are furthermore known from US 2003/0043359 A1 and U.S. Pat. No. 5,896,438.